Screw



(No Model.)

G. W. JACKMAN.

SCREW.

No. 306,492. Patented 00u14, 1884.

N. Pneus. mmmmmmr. www; n. c

invented a new 5 driver, the former being ETF@ TTES Farrar trice..

GEORGE XV. JACKMAN, OF LITTLETON, NEXT HABIIPSHIR'E.

SPECIFICATION forming part of Letters. Patent No. 306,492, dated October 14, 1884. Avplieation filed February 16, 18784. (X0 model.)

To all whom, it mfr/ y concern,.-

Be it known that l, GEORGE W. JMJKMAN, of the village of Littleton, inthe count-y of Grafton and State of Nei` Hampshire, have and useful Improvement in food-Screws, oi' which the following is a speciiication.

The invention relates to the means by which screws may be grasped and held by the screwdriver; and it consists of a screw having two nicks of sufficient depth across the head ofthe screw, contiguous to each other, and widened at the bottom,each in the direction ofthe other,so as to leave intact an intermediate portion 0i the screw-l1ead extending across the latter through its greatest diameter, and forming a spine wider at its crown than at its base, in such manner that the jaws of the screw-driver maybe inserted into the nicks and closed upon the spine.

In the accompanying drawings, in which similar letters of reference indicate like parts, Figure l represents the upper surface of the head of the screw, the same being indicated by the letter A, the nicks by the letters a a, and the spine by the letter b.

Fig. 2 represents a section of the head of the screw transverse to the spine and nicks, and shows the spine engaged by the jaws of the screw driver, A indicating' the screwhead, a a the nicks, l the spine, of which b is the crown, and b2 the base, and c c the jaws of the screw-driver.

Fig. 3 represents an entire screw and screwgrasped by the latter. lu this figure, A indicates the head ofthe screw, B, the blank, and C the threaded portion. a a are the nicks, and b the spine. D indicates the screw-driver, of which e is the handle, f j the jaws, j" f notches in the extremities thereof, g a lever for opening the jaws, and

. h a slide for confining the end of the lever.

1i represents a like section of the screw l head as that shown in Fig. 2, but with a different mode of widening the nicks at the bottom, and thereby diminishing the thickness of thebase of the spine, and also with the cxtremities of the jaws of the screw-driver made to correspond with these variations in the nicks and spine. In this figure, a a indicate the nicks, Z) the spine, b its crown, and b2 its base, and ff the extremities of the jaws oi'the screw-driver.

It will be observed that Figs. 2 and 3 represent thc spine as being diminished inthickness at its base by rectangular cuts into its sides; but this inode of accomplishing the desired end, which is that of giving a firm hold to the screw-driver upon the spine, is not essential; but this may be accomplished in the way indicated in Fig. 4, or by corrugating the sides of the spine, or in any other convenient way. rlhe essential thing is such a construction of the spine, substantially as indicated, as to give the required tenacity and firmness to the hold of the screwdriver.

rlhe advantages claimed for this invention are, in part, the greater facility thereby offered for grasping, holding, and controlling the screw and forcing it into position, and the diminution of the liability of thehead of the screw to break by bringing the greater part of the strain of driving upon the spine, which by its formation and position is best capable of bearing it, while at the same time a part of the strain is distributed to the portions of the screw-head outside the nieks,thus giving four bearings to the screw-driver.

XV hat is claimed as new and patentable in this invention isand a spine, b, all substantially as described.

GEORG-E XV. JAGKMAN. Vitnesses:

EDWARD JORDAN, Linus Hmm-reuse.

A screw having two nicks, a a, in the head, 

